On 2020-06-18 16:39, Marek Szyprowski wrote:
It is a common operation done by DRM drivers to check the contiguity of the DMA-mapped buffer described by a scatterlist in the sg_table object. Let's add a common helper for this operation.Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com> --- drivers/gpu/drm/drm_gem_cma_helper.c | 23 +++-------------------- drivers/gpu/drm/drm_prime.c | 26 ++++++++++++++++++++++++++ include/drm/drm_prime.h | 2 ++ 3 files changed, 31 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c index 06a5b9ee1fe0..41566a15dabd 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -471,26 +471,9 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev, { struct drm_gem_cma_object *cma_obj;- if (sgt->nents != 1) {- /* check if the entries in the sg_table are contiguous */ - dma_addr_t next_addr = sg_dma_address(sgt->sgl); - struct scatterlist *s; - unsigned int i; - - for_each_sg(sgt->sgl, s, sgt->nents, i) { - /* - * sg_dma_address(s) is only valid for entries - * that have sg_dma_len(s) != 0 - */ - if (!sg_dma_len(s)) - continue; - - if (sg_dma_address(s) != next_addr) - return ERR_PTR(-EINVAL); - - next_addr = sg_dma_address(s) + sg_dma_len(s); - } - } + /* check if the entries in the sg_table are contiguous */ + if (drm_prime_get_contiguous_size(sgt) < attach->dmabuf->size) + return ERR_PTR(-EINVAL);/* Create a CMA GEM buffer. */cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size); diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index bbfc713bfdc3..0784969894c1 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -825,6 +825,32 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page } EXPORT_SYMBOL(drm_prime_pages_to_sg);+/**+ * drm_prime_get_contiguous_size - returns the contiguous size of the buffer + * @sgt: sg_table describing the buffer to check + * + * This helper calculates the contiguous size in the DMA address space + * of the the buffer described by the provided sg_table. + * + * This is useful for implementing + * &drm_gem_object_funcs.gem_prime_import_sg_table. + */ +unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt) +{ + dma_addr_t expected = sg_dma_address(sgt->sgl); + struct sg_dma_page_iter dma_iter; + unsigned long size = 0; + + for_each_sgtable_dma_page(sgt, &dma_iter, 0) { + if (sg_page_iter_dma_address(&dma_iter) != expected) + break; + expected += PAGE_SIZE; + size += PAGE_SIZE;
Hmm, in many cases this is likely to be far less efficient than simply using for_each_sgtable_dma() and sg_dma_len() equivalent to the original implementation, and there doesn't seem to be any good reason for that. Plus AFAICS it could potentially let false-positives through if someone were to pass in a table with non-page-aligned lengths (I assume that's expected never to happen, but still...)
Robin.
+ } + return size; +} +EXPORT_SYMBOL(drm_prime_get_contiguous_size); + /** * drm_gem_prime_export - helper library implementation of the export callback * @obj: GEM object to export diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h index 9af7422b44cf..47ef11614627 100644 --- a/include/drm/drm_prime.h +++ b/include/drm/drm_prime.h @@ -92,6 +92,8 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, int flags);+unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt);+ /* helper functions for importing */ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, struct dma_buf *dma_buf,
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